Algernon’s deceptions are less serious than Jack’s. He appears never to hurt anyone with his fiction of Bunbury. He keeps his imaginary creation is kept at arm’s length; he does not actually pretend to be Bunbury. His motive for creating Bunbury appears to be to have an excuse to escape from tiresome duties and responsibilities in town, such as dining with Lady Bracknell. Because Algernon pretends that he goes to the country to look after the invalid Bunbury, he gains the additional benefit of borrowing the appearance of dutiful and charitable behavior. Algernon only adopts the persona of Ernest in order to meet Cecily, dropping the pretence immediately Cecily challenges him and honestly confessing his motive.
Jack, on the other hand, does pretend actually to be someone he is not. His motives for pretending to be Ernest in town are never made explicit, but the audience of Wilde’s time would naturally assume that Jack is an adherent of that by-product of strict Victorian morality, the double life. They would assume that Jack, under his false identity in town, gets up to the kinds of mischief and dissolute behavior of which respectable society disapproved. Blaming his wicked brother “Ernest” for his town activities, Jack is able to preserve the appearance of moral impeccability at his estate in the country. He is known only as a morally upright guardian to Cecily and a Justice of the Peace (judge) to the wider community, not to mention a concerned and dutiful brother to the reprobate Ernest.
Jack deceives even those closest to him. Both Algernon and Gwendolen, the woman whom Jack wants to marry, initially know him as Ernest. Jack’s deception comes under pressure when Gwendolen turns out to be irrevocably attached to the idea of marrying someone called Ernest, meaning that Jack cannot carry out his plan to kill off his fictional brother. Jack never admits to Gwendolen the real reasons for his long-term pretence of being someone else; instead, he merely allows...